The present invention relates generally to grinding control systems, and more particularly, to an automatic feed control system for controlling the feed rate or advancement of the grinding wheel into the workpiece so that the grinding rate of each workpiece is substantially constant as the final size is approached.
In the production grinding of succeeding workpieces, a rotating grinding wheel is initially advanced into a workpiece by feed means at a fast or coarse feed speed, whereby a relatively large amount of material is quickly removed. After the workpiece has been ground to a predetermined size, the rate of feed is reduced to a slower fine feed speed. When the workpiece is slightly larger than its final predetermined size, operation of the feed means is terminated. The grinding wheel, however, continues to advance into the workpiece and remove material as a result of pressure that developed as the grinding wheel and the workpiece were moved together by the feed means. At the precise moment the final size is attained, the grinding wheel is retracted. By terminating the operation or advancement of the feed means at a selected size greater than the final workpiece size, a more accurate workpiece size can be achieved with an improved finish because the grinding wheel approaches final size at a relatively slow rate.
As succeeding workpieces are machined, the grinding wheel becomes dull and loaded and an increasing amount of pressure must be applied against the workpiece by the grinding wheel to remove material. Consequently, when the advancement of the feed means is terminated, the time span to attain final size is continually reduced for each succeeding workpiece as the increased pressure against the workpiece is dissipated. As a result, it is increasingly difficult to retract the grinding wheel at the precise moment that final size is attained. Further, when the grinding wheel is freshly dressed, a reduced amount of pressure is required to machine the workpiece and an excessive time span may exist between the termination of advancement of the feed means and the retraction of the grinding wheel resulting in under-utilization of grinding equipment.
A monitoring system, along with measuring gauges, is used to measure the workpiece during grinding and to control the various workpiece sizes at which the feed rate transitions occur. This type of monitoring system however, does not automatically compensate for the changing surface conditions of the grinding wheel as succeeding workpieces are ground.